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Integrate Azure AD B2C with ASP.NET MVC Web App

In the previous post, we have configured our Web API to rely on our Azure AD B2C IdP to secure it so only calls which contain a token issued by our IdP will be accepted by our Web API.

In this post we will build our first front-end application (ASP.NET MVC 5 Web App) which will consume the API endpoints by sending a valid token obtained from the Azure AD b2C tenant, as well it will allow anonymous users to create profiles, and sign in against the Azure B2C tenant. The MVC Web app itself will be protected as well by the same Azure AD B2C tenant as we will share the same tenant Id between the Web API and MVC Web app.

So let’s start building the MVC Web App.

Step 1: Creating the MVC Web App Project

Let’s add a new ASP.NET Web application named “AADB2C.WebClientMvc” to the solution named “WebApiAzureAcitveDirectoryB2C.sln”, then add new MVC ASP.NET Web application, the selected template for the project will be “MVC”, and do not forget to change the “Authentication Mode” to “No Authentication” check the image below:

Once the project has been created, click on it’s properties and set “SSL Enabled” to “True”, copy the “SSL URL” value and right lick on project, select “Properties”, then select the “Web” tab from the left side and paste the “SSL URL” value in the “Project Url” text field and click “Save”. We need to allow https scheme locally once we debug the application. Check the image below:

Step 2: Install the needed NuGet Packages to Configure the MVC App

We need to add bunch of NuGet packages, so Open NuGet Package Manager Console and install the below packages:

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Install-PackageMicrosoft.Owin.Security.OpenIdConnect -Version3.0.1

Install-PackageMicrosoft.Owin.Security.Cookies -Version3.0.1

Install-PackageMicrosoft.Owin.Host.SystemWeb -Version3.0.1

Update-packageMicrosoft.IdentityModel.Protocol.Extensions

The package “Microsoft.Owin.Security.OpenIdConnect” contains the middleware used to protect web apps with OpenId Connect, this package contains the logic for the heavy lifting happens when our MVC App will talk with Azure B2C tenant to request tokens and validate them.

The package “Microsoft.IdentityModel.Protocol.Extension” contains classes which represent OpenID Connect constants and messages, lastly the package “Microsoft.Owin.Security.Cookies” will be used to create a cookie based session after obtaining a valid token from our Azure AD B2C tenant. This cookie will be sent from the browser to the server with each subsequent request and get validate by the cookie middleware.

Step 3: Configure Web App to use Azure AD B2C tenant IDs and Policies

Now we need to modify the web.config for our MVC App by adding the below keys, so open Web.config and add the below AppSettings keys:

The usage for the each setting has been outlined in the previous post, the only 2 new settings keys are: “ida:RedirectUri” which will be used to set the OpenID connect “redirect_uri” property The value of this URI should be registered in Azure AD B2C tenant (we will do this next), this redirect URI will be used by the OpenID Connect middleware to return token responses or failures after authentication process, as well after the sign out process. The second setting key “api:OrdersApiUrl” will be used as a base URI for our Web API.

Now let’s register the new Redirect URI in Azure B2C tenant, to do so login to Azure Portal and navigate to the App “Bit of Tech Demo App” we already registered in the previous post, then add the value “https://localhost:44315/” in the Reply URL settings as the image below, note that I already published the MVC web App to Azure App Services to the URL (https://aadb2cmvcapp.azurewebsites.net/) so I’ve included this URL too.

Step 4: Add Owin “Startup” Class

The default MVC template comes without a “Startup” class, but we need to configure our OWIN OpenID Connect middleware at the start of our Web App, so add a new class named “Startup” and paste the code below, there is a lot of code here so jump to the next paragraph as I will do my best to explain what we have included in this class.

// For each policy, give OWIN the policy-specific metadata address, and

// set the authentication type to the id of the policy

MetadataAddress=String.Format(aadInstance,tenant,policy),

AuthenticationType=policy,

// These are standard OpenID Connect parameters, with values pulled from web.config

ClientId=clientId,

RedirectUri=redirectUri,

PostLogoutRedirectUri=redirectUri,

Notifications=newOpenIdConnectAuthenticationNotifications

{

AuthenticationFailed=AuthenticationFailed

},

Scope="openid",

ResponseType="id_token",

// This piece is optional - it is used for displaying the user's name in the navigation bar.

TokenValidationParameters=newTokenValidationParameters

{

NameClaimType="name",

SaveSigninToken=true//important to save the token in boostrapcontext

}

};

}

}

What we have implemented here is the following:

From line 4-12 we have read the app settings for the keys we have included in MVC App web.config where they represent Azure AD B2C tenant and policy names, note that policy names access modifiers are set to public as it will be referenced in another class.

Inside the method “ConfigureAuth” we have done different things as the following:

Line
app.SetDefaultSignInAsAuthenticationType(CookieAuthenticationDefaults.AuthenticationType) will configure the OWIN security pipeline and inform the OpenID connect middleware that the default authentication type we will use is”Cookies”, and this means that the “Claims” encoded in the token we will receive from Azure AD B2C tenant will be stored in a Cookie (Session for the authenticated user).

Line
app.UseCookieAuthentication(newCookieAuthenticationOptions()); will register a cookie authentication middleware instance with default options, this means that Authentication type here is equivalent to the same authentication type we set in the previous step. it will be “Cookies” too.

Lines
app.UseOpenIdConnectAuthentication are used to configure the OWIN security pipeline to use the authentication provider (Azure AD B2C) per policy, in our case, there will be 3 different policies we already defined.

The method
CreateOptionsFromPolicy will take the Policy name as input parameter and will return an object of type “OpenIdConnectAuthenticationOptions”, This object is responsible for controlling the OpenID Connect middleware. The properties we used to configure the instance of “OpenIdConnectAuthenticationOptions” as the below:

The
MetadataAddress property will accept the address of the discovery document endpoint for our Azure AD B2C tenant per policy, so for example, the discovery endpoint for policy “B2C_1_Signup” will be “https://login.microsoftonline.com/BitofTechDemo.onmicrosoft.com/v2.0/.well-known/openid-configuration?p=B2C_1_Signup”. This discovery document will be used to get information from Azure AD B2C on how to generate authentication requests and validated incoming token responses.

The
AuthenticationType property will inform the middleware that authentication operation used is the policies we already defined, so for example if you defined a forth policy and you didn’t register it with the OpenID connect middleware, the tokens issues by this policy will be rejected.

The
ClientId property will tell Azure AD B2C which ID to use to match the requests originating from the Web App. This will represent the Azure AD B2C tenant we defined earlier in the previous posts.

The
RedirectUri property will inform the Azure AD B2C where your app wants the requested token response to be returned to, the value of this URL should be registered previously in the “ReplyURLs” values in Azure AD B2C App we defined earlier.

The
PostLogoutRedirectUri property will inform Azure AD B2C where to redirect the browser after a sign out operation completed successfully.

The
Scope property will be used to inform our Azure AD B2C tenant that our web app needs to use “OpenId Connect” protocol for authentication.

The
ResponseType property will indicate what our Web App needs from Azure AD B2C tenant after this authentication process, in our case, we only need an
id_token

The
TokenValidationParameters is used to store the information needed to validate the tokens, we only need to change 2 settings here, the
NameClaimType and the
SaveSigninToken . Setting the “NameClaimType” value to “name” will allow us to read the display name of the user by calling
User.Identity.Name , and setting the “SaveSigninToken” to “true” will allow us to save the token we received from the authentication process in the claims created (Inside the session cookie), this will be useful to retrieve the token from the claims when we want to call the Web API. Keep in mind that the cookie size will get larger as we are storing the token inside it.

Lastly, the property
Notifications will allow us to inject our custom code during certain phases of the authentication process, the phase we are interested in here is the
AuthenticationFailed phase, in this phase we want to redirect the user to the root directory of the Web App in case he/she clicked cancel on the sign on or sign in forms, and we need to redirect to the error view if we received any other exception during the authentication process.

This was the most complicated part in configuring our Web App to use our Azure AD B2C tenant. Now the next steps should be simpler and we will modify some views and add some new actions to issue requests to our Web API and call the Azure AD B2C polices.

Step 5: Call the Azure B2C Polices

Now we need to configure out Web App to invoke the policies we created, to do so we need to add a new controller named “AccountController”, so add it and paste the code below:

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publicclassAccountController:Controller

{

publicvoidSignIn()

{

if(!Request.IsAuthenticated)

{

// To execute a policy, you simply need to trigger an OWIN challenge.

// You can indicate which policy to use by specifying the policy id as the AuthenticationType

What we have implemented here is simple, and it is the same for actions
SignIn ,
SignUp , and
Profile , what we have done is a call to the
Challenge method and specify the related Policy name for each action.

The “Challenge” method in the OWIN pipeline accepts an instance of the object
AuthenticationProperties() which is used to set the settings of the action we want to do (Sign in, Sign up, Edit Profile). We only set the “RedirectUri” here to the root path of our Web App, taking into consideration that this “RedirectUri” has nothing to do with the “RedirectUri” we have defined in Azure AD B2C. This can be a different URI where you want the browser to redirect the user only after a successful operation takes place.

Regarding the
SignOut action, we need to Signout the user from different places, one by removing the app local session we created using the “Cookies” authentication and the other one by informing the OpenID connect middleware to send a Sign out request message to our Azure AD B2C tenant so the user is signed out from there too, that’s why we are retrieving all the Auth types available for our Web App and then we pass those different authentication types to the the “SignOut” method.

Now let’s add a partial view which renders the links to call those actions, so add a new partial view named “_LoginPartial.cshtml” under the “Shared” folder and paste the code below:

Notice that part of partial view will be rendered only if the user is authenticated and notice how we are displaying the user “Display Name” from the claim named “name” by only calling
@User.Identity.Name

Now we need to reference this partial view in the “_Layout.cshtml” view, we need just to replace the last Div in the body section with the below section:

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<div class="navbar-collapse collapse">

<ul class="nav navbar-nav">

<li>@Html.ActionLink("Home", "Index", "Home")</li>

<li>@Html.ActionLink("Orders List", "Index", "Orders")</li>

</ul>

@Html.Partial("_LoginPartial")

</div>

Step 6: Call the Web API from the MVC App

Now we want to add actions to start invoking the protected API we’ve created by passing the token obtained from Azure AD B2C tenant in the “Authorization” header for each protected request. We will add support for creating a new order and listing all the orders related to the authenticated user. If you recall from the previous post, we will depend on the claim named “objectidentifer” to read the User ID value encoded in the token as a claim.

To do so we will add a new controller named “OrdersController” under folder “Controllers” and will add 2 actions methods named “Index” and “Create”, add the file and paste the code below:

We have added an
[Authorize] attribute on the controller so any unauthenticated (anonymous) request (Session cookie doesn’t exist) to any of the actions in this controller will result into a redirect to the Sign in policy we have configured.

Notice how we are reading the
BootstrapContext from the current “ClaimsPrincipal” object, this context will contain a property named “Token” which we will send in the “Authorization” header for the Web API. Note that if you forgot to set the property “SaveSigninToken” of the “TokenValidationParameters” to “true” then this will return “null”.

We are using HTTP Client to craft the requests and call the Web API endpoints we defined earlier. There is no need to pay attention to the User ID property in the MVC App as this property is encoded in the token itself, and the Web API will take the responsibility to decode it and store it in the Azure table storage along with order information.

Step 7: Add views for the Orders Controller

I will not dive into details here, as you know we need to add 2 views to support rendering the list of orders and creating a new order, for sake of completeness I will paste the cshtml for each view, so open a new folder named “Orders” under “Views” folder, then add 2 new views named “Index.cshtml” and “Create.cshtml” and paste the code as the below:

Step 8: Lastly, let’s test out the complete flow

To test this out the user will click on “Orders List” link from the top navigation menu, then he will be redirected to the Azure AD B2C tenant where s/he can enter the app local credentials, if the crednetials provided are valid then a successful authentication will take place and a token will be obtained and stored in the claims identity for the authenticated user, then the orders view are displayed the token is sent in the authorization header to get all orders for this user. It should be something as the animated image below:

That’s it for now folks, I hope you find it useful 🙂 In the next post, I will cover how to integrate MSAL with Azure AD B2C and use it in a desktop application. If you find the post useful; then do not forget to share it 🙂

Thanks for this example.
I am using on-premises ADFS and am having trouble signing out of my web application. I tried your code but the cookies are not consistently being deleted in the SignOut method. I think this should work the same as your azure example. For sure the SignOut method is not logging me out of ADFS since I can delete all cookies in the browser manually and when I go to my site and get redirected to ADFS, I get a new cookie without logging in.

Hi John,
I need to check what has been changed on Azure B2C as the pace for updates on Azure is very quick, sure thing I will consider this soon, I believe things would be easier with SPAs when MS release MSAL.

So I am able to get the token back and if I subclass my own JwtSecurityTokenHandler and use that as part of the handler collection, it fails in ResolveIssuerSigningKey(), it returns null instead of a security token.

It had to do with the metadata endpoint in the token parameters. I had removed the ?p={policy} from the querystring and added it instead in the RedirectToIdentityProvider notification of the OpenIdConnectAuthenticationOptions. Well, apparently, somewhere in the vastness of the middleware. it uses that MetadataAddress string to retrieve the security keys and doesn’t respect that which is returned by RedirectToIdentityProvider.

Thanks. Very good article.
I have a query. Say, I have an Web APP registered under Azure AD B2C and protected. How I can enable SSO for on-premise users whose user ID are on premise AD. Say an on premise user logged into his workstation (within on premise network) with his user ID. In a later point in time, he is trying to access the Web App which is registered under Azure AD B2C. He should not be prompted to key in the user id and Password. He should be able to access the Web APP with his already logged in ID. What are the option to achieve this single sign on.
Thanks and Regards
Ambareesh

Hello Ambareesh,
Thanks for your comment, if I understood your question correctly, I do not believe this doable, you have a missing requirement here, so let me ask you, is there any relation between on-premise AD and Azure AD B2C? Well, I believe there is nothing, so how the identity of the on-prem user will be used in Azure B2C?
If I didn’t get your correctly please elaborate more to check this issue.

Hello Taiseer,
Thank you for your time in replying to my query. The requirement is as below.
I have a Web APP and Web API hosted on Azure protected by Azure AD B2C. If that same application (Web APP and Web API) has to be accessed by users who are in another AD, what are the options? Is that the application has to be registered in that AD as well? Can that same application accepts token from different Identity provider’s?
With Best Regards
Ambareesh